TID, TLH, TMI, TDA and TWP content

I'm going to use rinadragomir's post which is this one

Why do I think Charles is possibly the ghost

We know it's a him: so Charles

He reacted very violently to being called Matthew Fairchild, which would make sense, because he wouldn't want to be mistaken by his brother

He obviously knows the merry thieves too well

Connected to the Castairs by Alastair, who I think really never got over. That would also explain the dagger, and why the ghost reacted like that to it.

Cassie said the ghost was from the old books, like TID. Well, maybe she ment that he's from old books, as in, books from the 1900? Charles is also at the end of Clockwork Princess, maybe it counts? My theory has flaws, I know👌🏾

Not the best perosnalty, but trying to be useful? Charles. Maybe he realised he's a bigger worm than Benedict and decided to try to make things right, but a little late? So now he has to do it on a ghost form.

He is obviously connect to the Lightwoods, and he was Grace Blackthorn's fiance, thought it doesn't seem like that big of a deal for him to be imprisoned in the blackthorn manner. Maybe it is because something that happens in chot?